Explosive container with yieldable seal



y 5, 1965 J. F. HAMILTON 3,185,092

EXPLOSIVE CONTAINER WITH YIELDABLE SEAL Filed Jan. 10, 1964 2 JOHN F.HAMILTON INVENTOR.

United States Patent This invention relates to an explosive columnassembly especially adapted for use in seismiooperations and moreparticularly to an improved explosive column assembly and plasticexplosive containers therefor.

The explosives industry has for many years packaged explosives in paper,metal and plastic containers, all of which have been provided withvarious types of coupling means for forming an explosive column. On acommercial basis, only the paper and metal containers have found wideacceptance primarily due to the economic factors involved when usingplastic. Paper containers have been most Widely accepted in view oftheir versatility for handling both sensitive and insensitiveexplosives, although paper containers require a considerable amount ofwater-proofing and wall thickness to insure a substantially rigidexplosive column. Metal containers have been widely accepted in view oftheir strength, waterproofness and ease of providing coupling meanstherefor; however, they have been limited to the packaging of relativelyinsensitive explosives in view of the hazards involved in packaging andsealing sensitive explosives in metal. Plastic containers have notheretofore been appreciably accepted in view of the economic factorsmentioned although it has long been realized that the material possessedmany advantages, particularly in respect to waterproofness and safetyfor the packaging of sensitive as well as insensitive explosives.

Therefore, it is a principal object of the present invention to provideplastic containers which may be manufactured in an efficient andeconomical manner and which containers may be assembled in a facile,efficient and economical manner. Moreover, a further object is toprovide additional desirable features heretofore not available to theart such as placing the packaged explosive under compressive forceduring assembly where if the container is not properly filled or if thecolumn tends to elongate, improved contact between adjacent explosivecharges is insured with attendant consistency of propagation rate.

Other objects of the invention will appear hereinafter, the novelfeatures and combinations being set forth in the appended claims.

Generally described, the present invention comprises an explosive columnassembly having a plurality of substantially cylindrical blown plasticcontainers charged with explosive, each of said container having athreaded male coupling and end closure at one end and a threaded femalecoupling and yieldable seal adjacent the explosive at the other end, andsaid containers being threadedly interconnected by said male and femalecouplings and having the end closures of the male couplings exertingcornpressive force on the yieldable seals and adjacent explosive of thefemale couplings. In a more specific aspect in accordance with thepresent invention, there is provided a container for explosives, adaptedfor interconnection with like containers to form an explosive columnassembly, which comprises a thin-wall elongated substantiallycylindrical blown plastic container having explosive disposed thereinthroughout the major length of the container and having a yieldable sealwithin the container adjacent the explosive, an externally threaded malecoupling and end closure in the thin wall on one end of the container,an internally threaded female cou- 3,185,92 Fatented May 25, 1965 plingin the thin wall on the other end of the container, the female couplingextending beyond the yieldable seal the remaining length of thecontainer, and the male coupling having a reduced external diameterrelative to the internal diameter of the female coupling whereby likecontainers of explosive may be threadedly interconnected by the male andfemale couplings to form an explosive column assembly having the endclosures of the male couplings exerting compressive force on theyieldable seals and adjacent explosive of the female couplings.

A preferred embodiment of the invention has been chosen for purposes ofillustration and description and is shown in the accompanying drawingswhere reference symbols refer to like parts Wherever they occur.

FIG. 1 is an elevational view of a container in accordance with theinvention with a part thereof in section showing the yieldable seal andadjacent explosive within the container;

FIG. 2 is a sectional view taken along line 22 of FIG. 1; and

FIG. 3 is a fragmentary part elevational and part sectional view showingthe interconnection of the containers of FIG. 1 to form an explosivecolumn assembly.

With reference to the drawings, a thin-wall elongated blown plasticcontainer 1 has an explosive 2 disposed therein throughout the majorlength of the container. A yieldable seal 3 is provided within thecontainer 1 adjacent the explosive 2. A double lead externally threadedmale coupling 4 with a rounded thread and standard pitch of 29 and aconvex end closure 5 are formed as a unitary structure in the thin wallat one end of the container 1 and the explosive 2 extends throughout thelength of the coupling. An internally threaded female coupling 6 withthreads compatible to the male coupling is formed in the thin wall onthe other end of the container 1 and extends substantially beyond theyieldable seal 3 and the explosive 2 positioned adjacent thereto. Themale coupling 4 has a reduced external diameter relative to the internaldiameter of the female coupling 6 with a transition taper 7 beingprovided in the thin wall of the container 1 to accomplish this. Therelationship between the diameters of the couplings is such as to insurea snug and yet easily rotatable threading. The threaded female coupling6 has double lead internal threads 8 positioned in the midportion of thecoupling. This arrangement facilitates the insertion of the malecoupling of a like container since the unthreaded extending portion ofthe coupling 6 serves as a guiding sleeve for proper engagement of thethreaded couplings and adds rigidity to the explosive column assembly.The arrangement also reduces the number of turns required forinterconnection of like containers.

Referring now more particularly to FIG. 3, it will be appreciated that aconsiderable bending moment can occur in the coupling 6 particularlywhen several containers are interconnected in a horizontal position andthen lifted for insertion in a vertical borehole. Accordingly, fourequally spaced reinforcing fillets 9 are provided which extend acrossthe threads 8. For the same reason and to counteract unusual bendingmoments imparted to the body of the thin-wall container 1, a pluralityof longitudinal reinforcing ribs Ill is spaced circumferentially aboutand substantially coextensive with that portion of the body of thecontainer lying between the male coupling l and the female coupling 6.Additionally, a plurality of girth reinforcing ribs 11 is spaced alongthe length of the longitudinal ribs 19 to insure overall integrity ofthe body structure of the container 1 against deformation under variousconditions of manufacture and field handling. It has been found that thelongitudinal reinforcing ribs ll) should have a width of not more thanthe width of the areas 12 lying therebetween and that :3 ordinarily.three to five of the girth reinforcing ribs 11 spaced along the lengthof the longitudinal ribs give very satisfactory results for the averagesize of most commercial cartridges. Furthermore, the threaded portion ofthe male coupling 4 is greater than the threaded portion of the femalecoupling 6 to insure that in threadedly assembling a column of thecontainers 1, the convex end closure of the male coupling exerts apositive compressive force on the yieldable seal 3 and adjacentexplosive 2 of the female coupling of a like container. If the packagedexposive is soft,. the yieldable seal 3 will be depressed therein asillustrated particularly in FIG. 3 depicting the interconnection of twolike containers where 1a and its like parts represent a superjacentcontainer and 1 and its like parts represent the subjacent container. Ifthe packaged explosive is hard, there will be very little depression, ifany, of the yieldable seal 3. In any event, regardless of the exactheight to which the container is filled including vagaries in fillingheight during manufacture and possible subsequent shrinkage, acompensating adjustment insuring minimum proximity of explosive chargesis actually made in the field during assembly of the containers of thisinvention by the exertion ofthe compressive force heretofore discussed.This insures a consistent propagating relationship with consistency ofrate and quite advantageously is accomplished in the field at the timethe explosive column is being readied for use. Moreover, a tight seal iseffected as between adjacent containers as the female coupling beingslightly elastic has its end maintained in tension as it is forced toaccommodate the unthreaded portion of the male coupling. Since theinternal diameter of the female coupling is less than the unthreadedexternal diameter of the male coupling, upon engagement of the twocoupling's, the unthreaded outer portion of the female coupling isslightly expanded over the male coupling as it is completely threadedthereinto. Accordingly, since the expansion is small and the elasticlimit or yield point of the plastic not exceeded, the upper portion ofthe female coupling remains under tension to insure and maintain a tightwater-resistant seal between the couplings upon complete assembly; Thistight seal as depicted in FIG. 3 is substantially effortlessly obtaineddue to the mechanical advantage imparted by the inclined plane of thescrew coupling means.

The following example will serve to illustrate a commercially sizedpreferred embodiment of this invention. It is to be understood, however,that the scope of the invention is not limited thereby with respect tothe specific structure or to the explosive charges utilized.

- A series of thin-wall containers was formed by blowmoldinghigh-density polyethylene having a density of 0.962 and a nominal meltindex of 0.8 (I at 190 C.). These containers were molded in a split molddesigned to yield the structure heretofore described and illustrated asa preferred embodiment of the invention. Dimensions of the containerswere 22%" overall length, 2 body diameter, sixteen reinforcing ribs wideraised 2" around 2 diameter, male coupling 4%" long, threaded portion ofmale coupling 2 /2" with convex end closure extending and with onerounded thread per 1" with double lead, said thread having a rootdiameter of 2 /s. and external diameter of 2 /2", a female coupling 4%"long, threaded midportion of female coupling /z c. to c. of split doublelead thread wide and 7 deep with two filled each side, and a ribbed bodyportion. The ribbed body portion had five girth ribs 75 wide equallyspaced with the exception of a midportion 4" long wherein threelongitudinal ribs were omitted to provide a smooth area for labeling.The wall thickness of the body of the container including the femalecoupling, was approximately 40 mils, and the wall thickness of the malecoupling was approximately 55 mils. Programming was used during theblow-molding process dto obtain female couplings that were uniform inthickness and strength.

Each of these containers was charged with approximately 5 pounds ofexplosive composition consisting of 49.0% nitroglycerin, 1.5%nitrocotton, 36.0% sodium nitrate, 7.0% pulp, 3.0% coated cob meal, 2.0%starch, 0.5% bagasse and 1.0% chalk. This charge filled each containerto a height approximately level with the girth rib adjacent the femalecoupling. A cupped polyethylene sealing disk approximately 25 mils thickwas then placed over the explosive and snugly fitted into the annulargirth rib adjacent the female coupling. The containers thus manufacturedwere tested and initiated under conventionalt field conditions asexplosive column assemblies containing from two to ten containers ineach assembly. The tests were satisfactory in all respects withadditional advantages hereinafter set forth. 2

With reference to the foregoing, it will be appreciated that thecontainers of this invention may be formed from many of the plasticmaterials capable of being blown but that the economy of the materialwill largely dictate its use. Thus, although linear polyethylene ispreferred and has been found highly satisfactory, polyolefins generally,and copolymers and alloys thereof and other materials such as ABSterpolymer, plasticized vinyl chloride, plasticized vinyl chloride-vinylacetate copolymer and the like may be used. Also, it will be appreciatedthat in addition to the specific seismic explosive used in the example,other explosives of various types suitable for various other blastingpurposes may be used such as generally, gelatins, dynamites,permissibles, safety explosives, slurry explosives and the like.Moreover, distinct advantages inure when employing the present inventionfor aqueous slurry explosives which show a one inch or two inchpropagation gap under water, and for gelatin dynamites Where under veryhigh water pressure, the propagation gap is markedly reduced as comparedto that observed under low water pressure. Furthermore, in addition tothe polyethylene yieldable seal used in the example, other plastics suchas those set forth for the container and nonplastic seals may be usedincluding treated paper board, waxes, resins, waterproofing compounds,and the like. Also, the seal can be a plastic cup sealed around its lipand the shell body with a hot melt adhesive, or a wax such as paraffin,or resins or asphaltic compounds or the like where extreme waterproofness is desired. The essential thing is that the seals should beyieldable in respect to deflection or in respect to sliding along thewall of the container or otherwise yielding so that compressive force isgently but firmly developed with close proximity assured as betweenadjacent container explosive charges. Still further, although continuousmale and female threads have been depicted for the couplings, the termthreaded is meant to include interrupted threads, the essential featurebeing that suificient thread pitch be utilized to function with for wardprogression to insure compression as the couplings herein described.Moreover, although the reinforcing ribs have been described as raised,they may be obtained also by providing a constant body diameter with theareas such as 12 depressed, thus forming ribs such as 10 and 11.Ordinarily, the explosive containers of this invention are madeavailable in sizes from about 6 to about inches in length and from about1 to about 8 inches in diameter with the number of interconnected unitsdependent upon the specific service desired. Generally, for seismicWork, not more than about 10 units are used, and the 2 /2" x 22%"container herein specifically described has been found a popular size.In progressing to the larger sizes, an increase in the wall thickness ofthe plastic is ofcourse necessary but, nevertheless, due to the blownfeature and other structural features introduced by this invention, thewall thickness need be only slightly increased, not exceeding about 10to 25%, thus retaining efficient and economical manufacture.

The additional advantages previously referred to' in connection with theexample and field tests are as follows relative to prior art papercontainers since metal containers cannot be used for this typeexplosive: 15% more explosive energy obtained through using plasticshells; an increased overall specific gravity, which, coupled with thegplastic surface features, results in improved sinking rats, in drillmud, consequently reducing the need or poling; of charges; shorter shelllength per given weight of charge provides a more compact charge; thecharges in Soft containers are easier to prime for the shooter byconventional means; a screw type, positive coupling featitre makingassembly and disassembly a simpler task; in-

,creased protection to.,the powder charge because the plastic isimpervious to water; improved loading in boreholes due to flexibility asthe plastic assembly will yield and slide by obstructions; a plasticunit susceptible for use wherever paper containers or metalliccontainers formerly were preferred and in some instances unalterablynecessary; and a general purpose plastic unit which does not tend todisintegrate or rust internally in the presence of moisture or watercontaining explosives and does not tend to disintegrate or rust in thepresence of moisture or water as externally encountered inwater-containing boreholes and unsheltered storage.

From the foregoing, it will be evident to those skilled in the art thatvarious modifications can be made or followed, in the light of theforegoing disclosure and discussion, without departing fromthe spirit orscope of the disclosure or from the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A container for explosives adapted for interconnection with likecontainers to form an explosive column assembly, which comprises:

(a) la thin-wa1l elongated substantially cylindrical blown plasticcontainer having explosive disposed therein throughout the major lengthof the container and having a yieldable seal within the containeradjacent the explosive,

(b) an externally threaded male coupling and end closure in the thinwall on one end of the container,

(c) an internally threaded female coupling in the thin wall on the otherend of the container, .the female coupling extending beyond theyieldable seal the remaining length of the container, and

(d) the male coupling having a reduced external diameter relative to theinternal diameter of the female coupling and the end closure of saidmale coupling having protrusion means to contact and to force theyieldable seal of a like container into the explosive adjacent theretoso that like containers of explosive threadedly interconnected by themale and female couplings to form an explosive column. assembly have theend closures of the male cou plings exerting compressive force on theyieldable seals and adjacent explosive of the female couplings.

2. A container for explosives adapted for interconnection with likecontainers to form an explosive column assembly, which comprises:

(a) a thin-'wall elongated substantially cylindrical blown plasticcontainer having explosive disposed therein throughout the major lengthof the container and having .a yieldable seal within the containeradjacent the explosive,

(b) an externally threaded male coupling and end closure in the thinWall on one end of the container,

(c) an internally threaded female coupling in the thin Wall on the otherend of the container, the female coupling extending beyond the yieldableseal the remaining length of the container, said female coupling havinga threaded midportion only, and

(d) the male coupling having a reduced external diameter relative to theinternal diameter of the female coupling and the end closure of saidmale coupling having protrusion means to contact and to force theyieldable seal of a like container into the explosive adjacent theretoso that like containers of explosive threadedly interconnected by themale and female couplings to form an explosive column assembly have theend closures of the male couplings exerting compressive force on theyieldable seals and adjacent explosive of the female couplings. 3. Acontainer for explosives adapted for interconnection with likecontainers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plasticcontainer having explosivenisposed' therein throughout the major length.of the container and having a yieldable seal within the containeradjacent the explosive,

(b) an externally threaded male coupling and end closure in the thinWall on one end of the container,

(0) an internally threaded female coupling inthe thin wall on the otherend of the container, the female coupling extending beyond the yieldableseal the remaining length of the container, said female coupling havinga threaded midpo-rtion only, and said threaded midportion having atleast four equally spaced reinforcing fillets for each complete turnthereof extending across the threads, and

(d) the male coupling having a reduced external diameter relative to theinternal diameter of the female coupling and the end closure of saidmale coupling having protrusion means to contact and to force theyieldable seal of a like container into the explosive adjacent theretoso that like containers of explosive threadedly interconnected by themale and female couplings to form an explosive column assembly have theend closures of the male couplings exerting compressive force on theyieldable seals and adjacent explosive of the female couplings.

4. A container for explosives adapted. for interconnection with likecontainers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical :blown plasticcontainer having explosive dis-posed therein throughout the major lengthof the container and having a yieldable seal within the containeradjacent the explosive,

(b) an externally threaded male coupling and end closure in the thinwall on one end of the container,

(0) an internally threaded female coupling in thethin wall on the otherend of the container, the female coupling extending beyond theyield-able seal the remaining length of the container, said femalecoupling having a threaded midportion only, and said threaded midportionhaving at least four equally spaced reinforcing fillets for eachcomplete turn there-of extending across the threads,

(d) a plurality of longitudinal reinforcing ribs spacedcircumferentially about and substantially coextensive with that portionof the body of the container lying between the male coupling and thefemale coupling, and

(e) the male coupling having a reduced external diameter relative to theinternal diameter of the female coupling and the and closure of saidmale coupling having protrusion means to contact and to force theyieldable seal of a like container into the explosive adjacent theretoso that like containers of explosive threadedly interconnected by themale and female couplings to form an explosive column assembly have theend closures of the male coupl-rngs exerting compressive force on theyieldable seals and adjacent explosive of the female couplings.

5. A container for explosives adapted for interconnectron with likecontainers to form an explosive column assembly, which comprises:

(a) a thin-wall elongated substantially cylindrical blown plasticcontainer having explosive disposed therein throughout the major lengthof the container and having a yielda-ble seal within the containeradjacent the explosive,

(b)-|an'externallythreaded male coupling and end closure in the thinwall on one end of the container,

() an internally threaded female coupling in the thin wall on the otherend of the container, the female coupling extending beyond the yieldableseal the remaining length of the container, said female coupling havinga threaded midportion only, and said threaded midportion having at leastfour equally spaced reinforcing fillets for each complete turn thereofextending across the threads, and

(d) a plurality of longitudinal reinforcing ribs spacedcircumferentially about and substantlally coextensive with that portionof the body of the container lying between the male coupling and [thefemale coupling,

(e) 'a plurality of girth reinforcing ribs spaced along the length ofthe longitudinal reinforcing ribs, and (f)'the male coupling having areduced external diameter relative to the internal diameter of thefemale coupling and the end closure of said male coupling havingprotrusion means to contact and to force the yieldable seal of a likecontainer into the explosive adjacent thereto so that like containers ofexplosive thrcadedly interconnected by the male and female couplings toform an explosive column assembly have the-end closures of the malecouplings exerting compressive force on the yieldab'le seals andadjacent explosive of the female couplings. 6. A container forexplosives adapted for interconnection with like containers to form anexplosive column assembly, which comprises:

(a) la thin-wall elongated iblown polyethylene plastic container'havingexplosive material disposed therein throughout the major length of thecontainer and having a yieldable seal within the container adjacent theexplosive material, (b) -an externally threaded male coupling and endclosure blown asa unitary structure in the thin wall on one end of thecontainer, (c)-aninternal1y threaded fem-ale coupling blown in the thinwall on the other end of the container, the female coupling extendingbeyond the yield-able seal theremaining length of the container, saidfemale coupling having a threaded midportion only, and said threadedmidportion having at least four equally spaced rein-forcing fillets foreach complete t-urn thereof extending across the threads, and (d) a'plunality of longitudinally reinforcing ribs spaced circumferentia'llyabout and substantially coextensive with that port-ion of the body ofthe container lying between the male coupling and the female coupling,e) a plurality of girth reinforcing ribs spaced along the length of thelongitudinal reinforcing ribs, and (j) the male coupling having areduced external diameter relative to the internal diameter of thefemale coupling'and the end closure of said male i coupling havin-gprotrusion means to contact and to force the yieldable seal of a likecontainer into the explosive adjacent thereto so that like containers ofexplosive threadedly interconnected by the male and female couplings toform an explosive column assembly have the end closures of the male{couplings exerting compressive force on the yield ible seals andadjacent explosive of the female couplings.

7. The explosive cartridge according to claim 6 wherein the threadedportion of the male coupling ismore than twice the length of thethreaded'rnidportion of the female coupling.

8. The explosive cartridge according to claim 6 where in the end closureis convex and the threaded portion of the male coupling and the threadedmidportion of the female coupling have double lead threads.

9. The explosive cartridge according to claim 6 wherein the longitudinalreinforcing ribs have a width of not more than the width of the areaslying therebetween.

10. The explosive cartridge according to claim 6 wherein the blownpolyethylene plastic is high-density polyethylene characterized 'by adensity of 0.962 and a nominal melt index of 0.8.

11. An explosive column assembly comprising:

(a) a plurality of substantially cylindrical blown plastic containerscharged with explosive,

(b) each of said containers having a threaded male coupling and aprojected end closure having protrusion means atone end and a threadedfemale coupling' and yieldable 'seal adjacent the explosive at the otherend, and

' (c) said containers being threadedly interconnected I by said male andfemale couplings and having the protrusion means of the end closures ofthe male couplings exerting compressive (force on the yield- ;able sealsand-adjacent explosive of thefemale couplings. I

12. The explosive column assembly according to claim 11 wherein theplastic is high density polyethylene charagterized by a density of 0.962and a nominal melt index 0 0.8.

13. The explosive column assembly according to claim 11 wherein theupper portion of the female couplings is in tension about the upperportion of the male couplings said upper portion of the female couplingsbeing of slightly less diameter than said upper port-ion of the malecouplings so that said tens on is effected upon complete interconnectionof the couplings.

References Citedby the Examiner UNITED STATES PATENTS 1,037,709 9/12Zieg 285-401 1,940,657 12/33 Wood'fond 102--'43 2,345,887 4/44'R-othrock 102-24 2,383,542 8/45 Godfrey l02-24 2,500,276 3/50 Church285402 2,755,735 7/56 Hatter 10224 3,013,492 12/6'1 Sexton l02--24BENJAMIN A. BORCHELT, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,185,092 May 25, 1965 John F. Hamilton It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 3, line 11, for "exposive" read explosive column 8, line 27,strike out "a projected'h Signed and sealed this 7th day of December1965.,

(SEAL) Altest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A CONTAINER FOR EXPLOSIVES ADAPTED FOR INTERCONNECTION WITH LIKECONTAINERS TO FORM AN EXPLOSIVE COLUMN ASSEMBLY, WHICH COMPRISES: (A) ATHIN-WALL ELONGATED SUBSTANTIALLY CYLINDRICAL BLOWN PLASTIC CONTAINERHAVING EXPLOSIVE DISPOSED THEREIN THROUGHOUT THE MAJOR LENGTH OF THECONTAINER AND HAVING A YIELDABLE SEAL WITHIN THE CONTAINER ADJACENT THEEXPLOSIVE, (B) AN EXTERNALLY THREADED MALE COUPLING AND END CLOSURE INTHE THIN WALL ON ONE END OF THE CONTAINER, (C) AN INTERNALLY THREADEDFEMALE COUPLING IN THE THIN WALL ON THE OTHER END OF THE CONTAINER, THEFEMALE COUPLING EXTENDING BEYOND THE YIELDABLE SEAL THE REMAINING LENGTHOF THE CONTAINER, AND (D) THE MALE COUPLING HAVING A REDUCED EXTERNALDIAMETER RELATIVE TO THE INTERNAL DIAMETER OF THE FEMALE COUPLING AN THEEND CLOSURE OF SAID MALE COUPLING HAVING PROTRUSION MEANS TO CONTACT ANDTO FORCE THE YIELDABLE SEAL OF A LIKE CONTAINER INTO